The long-term goal of our research is to understand the molecular mechanisms by which phospholipase D (PLD) 1) regulates the G-protein coupled signaling cascade critical for phototransduction and 2) mediates the redirection of Golgi-derived vesicles for membrane biogenesis during cellularization in Drosophila melanogaster. PLD hydrolyzes phosphatidylcholine to generate the lipid messenger, phosphatidic acid (PA). In mammalian systems, PLD has diverse functions, including vesicle trafficking, membrane formation, cytoskeletal rearrangements, and exocytosis. In yeast, PLD plays a critical role in membrane biogenesis during meiotic prospore membrane formation. The Specific Aims of this proposal are as follows: 1) determine the sub-cellular localization of dPLD in the eye and probe its role through gain- and loss-of-function analysis, 2) use mutant complementation to dissect genetically the function of dPLD in phototransduction, and 3) use marker co-localization, mutant complementation, and loss-of-function analysis to determine the function of PLD in cellularization.